Apparatus and methods for multi-antenna communications

ABSTRACT

Apparatus and methods for multi-antenna communications are provided. In certain embodiments, a communication system includes an antenna array including a plurality of antenna elements, and a plurality of RF circuit channels each coupled to a corresponding one of the antenna elements. The plurality of RF circuit channels generate two or more analog baseband signals in response to the antenna array receiving a radio wave. The communication system further includes a controllable amplification and combining circuit that generates two or more amplified analog baseband signals based on amplifying each of the two or more analog baseband signals with a separately controllable gain, and that combines the two or more amplified analog baseband signals to generate a combined analog baseband signal.

RELATED APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet, or any correction thereto,are hereby incorporated by reference into this application under 37 CFR1.57.

BACKGROUND Technical Field

Embodiments of the invention relate to electronic systems, and inparticular, to radio frequency (RF) electronics.

Description of Related Technology

A communication system can include a transceiver, a front end, and oneor more antennas for wirelessly transmitting and/or receiving signals.The front end can include low noise amplifier(s) for amplifyingrelatively weak signals received via the antenna(s), and poweramplifier(s) for boosting signals for transmission via the antenna(s).

Examples of communication systems include, but are not limited to,mobile phones, tablets, base stations, network access points,customer-premises equipment (CPE), laptops, and wearable electronics.

SUMMARY

In certain embodiments, the present disclosure relates to a radiofrequency system. The radio frequency system includes two or morefrequency downconverters configured to output two or more analogbaseband signals in response to receiving a plurality of radio frequencysignals from an antenna array. The radio frequency system furtherincludes a controllable amplification and combining circuit configuredto generate two or more amplified analog baseband signals based onamplifying each of the two or more analog baseband signals with aseparately controllable gain, and to combine the two or more amplifiedanalog baseband signals to generate a combined analog baseband signal.The radio frequency system further includes a data conversion and signalprocessing circuit configured to receive the combined signal.

In some embodiments, the controllable amplification and combiningcircuit is configured to generate the combined analog baseband signal ina first mode, and to output the two or more amplified analog basebandsignals in a second mode. According to a number of embodiments, theradio frequency system operates with beamforming in the first mode andwith diversity communications in the second mode.

In several embodiments, the controllable amplification and combiningcircuit includes two or more controllable gain input amplifiersconfigured to amplify the two or more analog baseband signals togenerate the two or more amplified analog baseband signals. Inaccordance with various embodiments, the controllable amplification andcombining circuit further includes two or more DC offset compensationcircuits each configured to provide a separately controllable DC offsetcorrection to a corresponding one of the two or more controllable gaininput amplifiers.

In some embodiments, the data conversion and signal processing circuitincludes two or more analog-to-digital converters each configured toreceive a corresponding one of the two or more amplified analog basebandsignals.

In various embodiments, the radio frequency system further includes twoor more local oscillators configured to control downconversion of thetwo or more frequency downconverters. According to a number ofembodiments, the two or more local oscillators each include aphase-locked-loop configured to receive a common timing referencesignal.

In certain embodiments, the present disclosure relates to a method ofradio frequency communication. The method includes receiving a radiowave using a plurality of antenna elements of an antenna array,generating two or more analog baseband signals using a plurality ofradio frequency circuit channels each coupled to a corresponding one ofthe plurality of antenna elements, amplifying each of the two or moreanalog baseband signals with a separately controllable gain using acontrollable amplification and combining circuit, and combining the twoor more amplified analog baseband signals to generate a combined analogbaseband signal using the controllable amplification and combiningcircuit.

In various embodiments, the method further includes generating thecombined analog baseband signal in a first mode of the controllableamplification and combining circuit, and outputting the two or moreamplified analog baseband signals in a second mode of the controllableamplification and combining circuit. According to a number ofembodiments, the method further includes forming a receive beam in thefirst mode and operating with diversity communications in the secondmode.

In a number of embodiments, the method further includes compensating fora DC offset of each of the two or more amplified analog basebandsignals.

In some embodiments, the method further includes converting the combinedanalog baseband signal to a digital signal.

In various embodiments, the method further includes performing phaseshifting in each of the radio frequency circuit channels at anintermediate frequency that is less than a frequency of the radio wave.

In several embodiments, the method further includes generating aplurality of clock signals using a plurality of local oscillatorsoperating with a common timing reference signal, and providing each ofthe plurality of clock signals to a corresponding one of the pluralityof radio frequency circuit channels.

In some embodiments, the method further includes generating a firstintermediate frequency signal using a first radio frequency circuitchannel of the plurality of radio frequency circuit channels, generatinga second intermediate frequency signal using a second radio frequencycircuit channel of the plurality of radio frequency circuit channels,and combining the first intermediate frequency signal and the secondintermediate frequency signal.

In certain embodiments, the present disclosure relates to acommunication system. The communication system includes an antenna arrayincluding a plurality of antenna elements, a plurality of radiofrequency circuit channels each coupled to a corresponding one of theplurality of antenna elements, and a controllable amplification andcombining circuit. The plurality of radio frequency circuit channels areoperable to generate two or more analog baseband signals in response tothe antenna array receiving a radio wave. Additionally, the controllableamplification and combining circuit is configured to generate two ormore amplified analog baseband signals based on amplifying each of thetwo or more analog baseband signals with a separately controllable gain,and to combine the two or more amplified analog baseband signals togenerate a combined analog baseband signal.

In various embodiments, the controllable amplification and combiningcircuit is configured to generate the combined analog baseband signal ina first mode, and to output the two or more amplified analog basebandsignals in a second mode. According to a number of embodiments, thecommunication system operates with beamforming in the first mode andwith diversity communications in the second mode.

In some embodiments, the controllable amplification and combiningcircuit includes two or more controllable gain input amplifiersconfigured to amplify the two or more analog baseband signals togenerate the two or more amplified analog baseband signals. According toa number of embodiments, the controllable amplification and combiningcircuit further includes two or more DC offset compensation circuitseach configured to provide a separately controllable DC offsetcorrection to a corresponding one of the two or more controllable gaininput amplifiers.

In several embodiments, the communication system further includes a dataconversion and signal processing circuit including two or moreanalog-to-digital converters each configured to receive a correspondingone of the two or more amplified analog baseband signals.

In a number of embodiments, the plurality of radio frequency circuitchannels each include a controllable phase shifter configured to providephase shifting at an intermediate frequency that is less than afrequency of the radio wave.

In some embodiments, the communication system further includes aplurality of local oscillators each configured to provide at least oneclock signal to a corresponding one of the plurality of radio frequencycircuit channels. According to various embodiments, the plurality oflocal oscillators each include a phase-locked-loop configured to receivea common timing reference signal.

In several embodiments, the plurality of radio frequency circuitchannels includes a first radio frequency circuit channel including afirst mixer configured to generate a first intermediate frequencysignal, and a second radio frequency circuit channel including a secondmixer configured to generate a second intermediate frequency signal.According to a number of embodiments, the communication system furtherincludes a combiner configured to generate a first analog basebandsignal of the two or more analog baseband signals based on combining thefirst intermediate frequency signal and the second intermediatefrequency signal.

In certain embodiments, the present disclosure relates to asemiconductor die. The semiconductor die includes a plurality ofcontrollable gain input amplifiers configured to amplify a plurality ofanalog baseband signals to generate a plurality of amplified analogbaseband signals, each of the plurality of controllable gain inputamplifiers configured to amplify a corresponding one of the plurality ofanalog baseband signals with a separately controllable amount of gain.The semiconductor die further includes a plurality of selection circuitseach configured to receive a respective one of the plurality ofamplified baseband signals, the plurality of selection signalsconfigured to combine the plurality of amplified analog baseband signalsto generate a combined analog baseband signal in a first mode, and tooutput the plurality of amplified analog baseband signals in a secondmode.

In a number of embodiments, the semiconductor die further includes aplurality of DC offset compensation circuits each configured to providea separately controllable DC offset correction to a corresponding one ofthe plurality of controllable gain input amplifiers.

In several embodiments, the plurality of selection circuits areimplemented as a plurality of cascode transistors.

In some embodiments, the plurality of controllable gain input amplifiersare implemented as a plurality of gain stages, the separatelycontrollable amount of gain based on a number of the plurality of gainstages that are selected. According to a number of embodiments, theplurality of gain stages are weighted.

In various embodiments, the semiconductor die further includes aplurality of output buffers each configured to buffer a correspondingone of the plurality of amplified analog baseband signals.

In several embodiments, the semiconductor die further includes aplurality of analog-to-digital converters each configured to provideanalog-to-digital conversion to a corresponding one of the plurality ofamplified analog baseband signals in the second mode. According to anumber of embodiments, a first analog-to-digital converter of theplurality of analog-to-digital converters is configured to provideanalog-to-digital conversion to the combined analog baseband signal inthe first mode. In accordance with various embodiments, one or more ofthe plurality of analog-to-digital converters are disabled in the firstmode to reduce power consumption.

In certain embodiments, the present disclosure relates to a method ofprocessing signals in a communication system. The method includesamplifying a plurality of analog baseband signals to generate aplurality of amplified analog baseband signals using a plurality ofcontrollable gain input amplifiers, including amplifying each of theplurality of analog baseband signals using a corresponding one of theplurality of controllable gain input amplifiers. The method furtherincludes separately controlling a gain of each of the plurality ofcontrollable gain input amplifiers. The method further includesprocessing the plurality of amplified analog baseband signals using asignal selector that includes a plurality of selection circuits eachreceiving a corresponding one of the plurality of amplified analogbaseband signals, including outputting a combined analog baseband signalin a first mode of the signal selector and outputting the plurality ofamplified analog baseband signals in a second mode of the signalselector.

In some embodiments, the method further includes providing DC offsetcorrection to the plurality of controllable gain input amplifiers usinga plurality of DC offset compensation circuits, including correcting aDC offset of each of the plurality of controllable gain input amplifiersusing a corresponding one of the plurality of DC offset compensationcircuits.

In various embodiments, separately controlling a gain of each of theplurality of controllable gain input amplifiers includes controlling anumber of active gain stages of each of the plurality of controllablegain input amplifiers.

In a number of embodiments, the method further includes buffering theplurality of amplified analog baseband signals.

In some embodiments, the method further includes providinganalog-to-digital conversion of the plurality of amplified analogbaseband signals using a plurality of analog-to-digital converters inthe second mode. In accordance with several embodiments, the methodfurther includes providing analog-to-digital conversion of the combinedanalog baseband signal using a first analog-to-digital converter of theplurality of analog-to-digital converters in the first mode. Accordingto a number of embodiments, the method further includes deactivating oneor more of the plurality of analog-to-digital converters in the firstmode.

In certain embodiments, the present disclosure relates to acommunication system. The communication system includes a plurality ofradio frequency circuit channels configured to output a plurality ofanalog baseband signals, and a controllable amplification and combiningcircuit including a plurality of controllable gain input amplifiersconfigured to amplify the plurality of analog baseband signals togenerate a plurality of amplified analog baseband signals, each of theplurality of controllable gain input amplifiers configured to amplify acorresponding one of the plurality of analog baseband signals with aseparately controllable amount of gain. The controllable amplificationand combining circuit further includes a plurality of selection circuitseach configured to receive a respective one of the plurality ofamplified baseband signals, the plurality of selection signalsconfigured to combine the plurality of amplified analog baseband signalsto generate a combined analog baseband signal in a first mode, and tooutput the plurality of amplified analog baseband signals in a secondmode.

In various embodiments, the controllable amplification and combiningcircuit further includes a plurality of DC offset compensation circuitseach configured to provide a separately controllable DC offsetcorrection to a corresponding one of the plurality of controllable gaininput amplifiers.

In a number of embodiments, the plurality of selection circuits areimplemented as a plurality of cascode transistors.

In several embodiments, the plurality of controllable gain inputamplifiers are implemented as a plurality of gain stages, and theseparately controllable amount of gain based on a number of theplurality of gain stages that are selected. In accordance with someembodiments, the plurality of gain stages are weighted.

In various embodiments, the controllable amplification and combiningcircuit further includes a plurality of output buffers each configuredto buffer a corresponding one of the plurality of amplified analogbaseband signals.

In some embodiments, the communication system further includes a dataconversion and signal processing circuit configured to receive thecombined analog baseband signal in the first mode, and the plurality ofamplified analog baseband signals in the second mode.

In several embodiments, the data conversion and signal processingcircuit includes a plurality of analog-to-digital converters eachconfigured to provide analog-to-digital conversion to a correspondingone of the plurality of amplified analog baseband signals in the secondmode. In accordance with a number of embodiments, a firstanalog-to-digital converter of the plurality of analog-to-digitalconverters is configured to provide analog-to-digital conversion to thecombined analog baseband signal in the first mode. According to variousembodiments, the one or more of the plurality of analog-to-digitalconverters are disabled in the first mode to reduce power consumption.

In some embodiments, the communication system further includes anantenna array including a plurality of antenna elements coupled to theplurality of radio frequency circuit channels.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of one example of a communication network.

FIG. 2A is a schematic diagram of one example of a downlink channelusing multi-input and multi-output (MIMO) communications.

FIG. 2B is schematic diagram of one example of an uplink channel usingMIMO communications.

FIG. 2C is schematic diagram of another example of an uplink channelusing MIMO communications.

FIG. 3A is a schematic diagram of one example of a communication systemthat operates with beamforming.

FIG. 3B is a schematic diagram of one example of beamforming to providea transmit beam.

FIG. 3C is a schematic diagram of one example of beamforming to providea receive beam.

FIG. 4A is a schematic diagram of one embodiment of a communicationsystem operating in a first mode.

FIG. 4B is a schematic diagram of the communication system of FIG. 4Boperating in a second mode.

FIG. 5A is a schematic diagram of a communication system according toanother embodiment.

FIG. 5B is a schematic diagram of a communication system according toanother embodiment.

FIG. 6A is a schematic diagram of one embodiment of a controllableamplification and combining circuit in a first mode of operation.

FIG. 6B is a schematic diagram of the controllable amplification andcombining circuit of FIG. 6A in a second mode of operation.

FIG. 7 is a schematic diagram of one embodiment of a portion of thecontrollable amplification and combining circuit of FIGS. 6A and 6B.

FIG. 8 is a schematic diagram of one embodiment of a DC offsetcompensation circuit.

FIG. 9A is a schematic diagram of a communication system according toanother embodiment.

FIG. 9B is a schematic diagram of one embodiment of a portion of thecommunication system of FIG. 9A.

FIG. 10 is a schematic diagram of one embodiment of a mobile device.

FIG. 11A is a perspective view of one embodiment of a module thatoperates with beamforming.

FIG. 11B is a cross-section of the module of FIG. 11A taken along thelines 11B-11B.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

The International Telecommunication Union (ITU) is a specialized agencyof the United Nations (UN) responsible for global issues concerninginformation and communication technologies, including the shared globaluse of radio spectrum.

The 3rd Generation Partnership Project (3GPP) is a collaboration betweengroups of telecommunications standard bodies across the world, such asthe Association of Radio Industries and Businesses (ARIB), theTelecommunications Technology Committee (TTC), the China CommunicationsStandards Association (CCSA), the Alliance for TelecommunicationsIndustry Solutions (ATIS), the Telecommunications Technology Association(TTA), the European Telecommunications Standards Institute (ETSI), andthe Telecommunications Standards Development Society, India (TSDSI).

Working within the scope of the ITU, 3GPP develops and maintainstechnical specifications for a variety of mobile communicationtechnologies, including, for example, second generation (2G) technology(for instance, Global System for Mobile Communications (GSM) andEnhanced Data Rates for GSM Evolution (EDGE)), third generation (3G)technology (for instance, Universal Mobile Telecommunications System(UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G)technology (for instance, Long Term Evolution (LTE) and LTE-Advanced).

The technical specifications controlled by 3GPP can be expanded andrevised by specification releases, which can span multiple years andspecify a breadth of new features and evolutions.

In one example, 3GPP introduced carrier aggregation (CA) for LTE inRelease 10. Although initially introduced with two downlink carriers,3GPP expanded carrier aggregation in Release 14 to include up to fivedownlink carriers and up to three uplink carriers. Other examples of newfeatures and evolutions provided by 3GPP releases include, but are notlimited to, License Assisted Access (LAA), enhanced LAA (eLAA),Narrowband Internet of things (NB-IOT), Vehicle-to-Everything (V2X), andHigh Power User Equipment (HPUE).

3GPP introduced Phase 1 of fifth generation (5G) technology in Release15, and plans to introduce Phase 2 of 5G technology in Release 16(targeted for 2019). Subsequent 3GPP releases will further evolve andexpand 5G technology. 5G technology is also referred to herein as 5G NewRadio (NR).

5G NR supports or plans to support a variety of features, such ascommunications over millimeter wave spectrum, beamforming capability,high spectral efficiency waveforms, low latency communications, multipleradio numerology, and/or non-orthogonal multiple access (NOMA). Althoughsuch RF functionalities offer flexibility to networks and enhance userdata rates, supporting such features can pose a number of technicalchallenges.

The teachings herein are applicable to a wide variety of communicationsystems, including, but not limited to, communication systems usingadvanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro,and/or 5G NR.

FIG. 1 is a schematic diagram of one example of a communication network10. The communication network 10 includes a macro cell base station 1, asmall cell base station 3, and various examples of user equipment (UE),including a first mobile device 2 a, a wireless-connected car 2 b, alaptop 2 c, a stationary wireless device 2 d, a wireless-connected train2 e, a second mobile device 2 f, and a third mobile device 2 g.

Although specific examples of base stations and user equipment areillustrated in FIG. 1 , a communication network can include basestations and user equipment of a wide variety of types and/or numbers.

For instance, in the example shown, the communication network 10includes the macro cell base station 1 and the small cell base station3. The small cell base station 3 can operate with relatively lowerpower, shorter range, and/or with fewer concurrent users relative to themacro cell base station 1. The small cell base station 3 can also bereferred to as a femtocell, a picocell, or a microcell. Although thecommunication network 10 is illustrated as including two base stations,the communication network 10 can be implemented to include more or fewerbase stations and/or base stations of other types.

Although various examples of user equipment are shown, the teachingsherein are applicable to a wide variety of user equipment, including,but not limited to, mobile phones, tablets, laptops, IoT devices,wearable electronics, customer premises equipment (CPE),wireless-connected vehicles, wireless relays, and/or a wide variety ofother communication devices. Furthermore, user equipment includes notonly currently available communication devices that operate in acellular network, but also subsequently developed communication devicesthat will be readily implementable with the inventive systems,processes, methods, and devices as described and claimed herein.

The illustrated communication network 10 of FIG. 1 supportscommunications using a variety of cellular technologies, including, forexample, 4G LTE and 5G NR. In certain implementations, the communicationnetwork 10 is further adapted to provide a wireless local area network(WLAN), such as WiFi. Although various examples of communicationtechnologies have been provided, the communication network 10 can beadapted to support a wide variety of communication technologies.

Various communication links of the communication network 10 have beendepicted in FIG. 1 . The communication links can be duplexed in a widevariety of ways, including, for example, using frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). FDD is a type ofradio frequency communications that uses different frequencies fortransmitting and receiving signals. FDD can provide a number ofadvantages, such as high data rates and low latency. In contrast, TDD isa type of radio frequency communications that uses about the samefrequency for transmitting and receiving signals, and in which transmitand receive communications are switched in time. TDD can provide anumber of advantages, such as efficient use of spectrum and variableallocation of throughput between transmit and receive directions.

In certain implementations, user equipment can communicate with a basestation using one or more of 4G LTE, 5G NR, and WiFi technologies. Incertain implementations, enhanced license assisted access (eLAA) is usedto aggregate one or more licensed frequency carriers (for instance,licensed 4G LTE and/or 5G NR frequencies), with one or more unlicensedcarriers (for instance, unlicensed WiFi frequencies).

As shown in FIG. 1 , the communication links include not onlycommunication links between UE and base stations, but also UE to UEcommunications and base station to base station communications. Forexample, the communication network 10 can be implemented to supportself-fronthaul and/or self-backhaul.

The communication links can operate over a wide variety of frequencies.In certain implementations, communications are supported using 5G NRtechnology over one or more frequency bands that are less than 6Gigahertz (GHz) and/or over one or more frequency bands that are greaterthan 6 GHz. For example, the communication links can serve FrequencyRange 1 (FR1), Frequency Range 2 (FR2), or a combination thereof. In oneembodiment, one or more of the mobile devices support a HPUE power classspecification.

In certain implementations, a base station and/or user equipmentcommunicates using beamforming. For example, beamforming can be used tofocus signal strength to overcome path losses, such as high lossassociated with communicating over high signal frequencies. In certainembodiments, user equipment, such as one or more mobile phones,communicate using beamforming on millimeter wave frequency bands in therange of 30 GHz to 300 GHz and/or upper centimeter wave frequencies inthe range of 6 GHz to 30 GHz, or more particularly, 24 GHz to 30 GHz.

Different users of the communication network 10 can share availablenetwork resources, such as available frequency spectrum, in a widevariety of ways.

In one example, frequency division multiple access (FDMA) is used todivide a frequency band into multiple frequency carriers. Additionally,one or more carriers are allocated to a particular user. Examples ofFDMA include, but are not limited to, single carrier FDMA (SC-FDMA) andorthogonal FDMA (OFDMA). OFDMA is a multicarrier technology thatsubdivides the available bandwidth into multiple mutually orthogonalnarrowband subcarriers, which can be separately assigned to differentusers.

Other examples of shared access include, but are not limited to, timedivision multiple access (TDMA) in which a user is allocated particulartime slots for using a frequency resource, code division multiple access(CDMA) in which a frequency resource is shared amongst different usersby assigning each user a unique code, space-divisional multiple access(SDMA) in which beamforming is used to provide shared access by spatialdivision, and non-orthogonal multiple access (NOMA) in which the powerdomain is used for multiple access. For example, NOMA can be used toserve multiple users at the same frequency, time, and/or code, but withdifferent power levels.

Enhanced mobile broadband (eMBB) refers to technology for growing systemcapacity of LTE networks. For example, eMBB can refer to communicationswith a peak data rate of at least 10 Gbps and a minimum of 100 Mbps foreach user. Ultra-reliable low latency communications (uRLLC) refers totechnology for communication with very low latency, for instance, lessthan 2 milliseconds. uRLLC can be used for mission-criticalcommunications such as for autonomous driving and/or remote surgeryapplications. Massive machine-type communications (mMTC) refers to lowcost and low data rate communications associated with wirelessconnections to everyday objects, such as those associated with Internetof Things (IoT) applications.

The communication network 10 of FIG. 1 can be used to support a widevariety of advanced communication features, including, but not limitedto, eMBB, uRLLC, and/or mMTC.

FIG. 2A is a schematic diagram of one example of a downlink channelusing multi-input and multi-output (MIMO) communications. FIG. 2B isschematic diagram of one example of an uplink channel using MIMOcommunications.

MIMO communications use multiple antennas for simultaneouslycommunicating multiple data streams over common frequency spectrum. Incertain implementations, the data streams operate with differentreference signals to enhance data reception at the receiver. MIMOcommunications benefit from higher SNR, improved coding, and/or reducedsignal interference due to spatial multiplexing differences of the radioenvironment.

MIMO order refers to a number of separate data streams sent or received.For instance, MIMO order for downlink communications can be described bya number of transmit antennas of a base station and a number of receiveantennas for UE, such as a mobile device. For example, two-by-two (2×2)DL MIMO refers to MIMO downlink communications using two base stationantennas and two UE antennas. Additionally, four-by-four (4×4) DL MIMOrefers to MIMO downlink communications using four base station antennasand four UE antennas.

In the example shown in FIG. 2A, downlink MIMO communications areprovided by transmitting using M antennas 43 a, 43 b, 43 c, . . . 43 mof the base station 41 and receiving using N antennas 44 a, 44 b, 44 c,. . . 44 n of the mobile device 42. Accordingly, FIG. 2A illustrates anexample of m×n DL MIMO.

Likewise, MIMO order for uplink communications can be described by anumber of transmit antennas of UE, such as a mobile device, and a numberof receive antennas of a base station. For example, 2×2 UL MIMO refersto MIMO uplink communications using two UE antennas and two base stationantennas. Additionally, 4×4 UL MIMO refers to MIMO uplink communicationsusing four UE antennas and four base station antennas.

In the example shown in FIG. 2B, uplink MIMO communications are providedby transmitting using N antennas 44 a, 44 b, 44 c, . . . 44 n of themobile device 42 and receiving using M antennas 43 a, 43 b, 43 c, . . .43 m of the base station 41. Accordingly, FIG. 2B illustrates an exampleof n×m UL MIMO.

By increasing the level or order of MIMO, bandwidth of an uplink channeland/or a downlink channel can be increased.

MIMO communications are applicable to communication links of a varietyof types, such as FDD communication links and TDD communication links.

FIG. 2C is schematic diagram of another example of an uplink channelusing MIMO communications. In the example shown in FIG. 2C, uplink MIMOcommunications are provided by transmitting using N antennas 44 a, 44 b,44 c, . . . 44 n of the mobile device 42. Additional a first portion ofthe uplink transmissions are received using M antennas 43 a 1, 43 b 1,43 c 1, . . . 43 m 1 of a first base station 41 a, while a secondportion of the uplink transmissions are received using M antennas 43 a2, 43 b 2, 43 c 2, . . . 43 m 2 of a second base station 41 b.Additionally, the first base station 41 a and the second base station 41b communication with one another over wired, optical, and/or wirelesslinks.

The MIMO scenario of FIG. 2C illustrates an example in which multiplebase stations cooperate to facilitate MIMO communications.

FIG. 3A is a schematic diagram of one example of a communication system110 that operates with beamforming. The communication system 110includes a transceiver 105, signal conditioning circuits 104 a 1, 104 a2 . . . 104 an, 104 b 1, 104 b 2 . . . 104 bn, 104 m 1, 104 m 2 . . .104 mn, and an antenna array 102 that includes antenna elements 103 a 1,103 a 2 . . . 103 an, 103 b 1, 103 b 2 . . . 103 bn, 103 m 1, 103 m 2 .. . 103 mn.

Communications systems that communicate using millimeter wave carriers(for instance, 30 GHz to 300 GHz), centimeter wave carriers (forinstance, 3 GHz to 30 GHz), and/or other frequency carriers can employan antenna array to provide beam formation and directivity fortransmission and/or reception of signals.

For example, in the illustrated embodiment, the communication system 110includes an array 102 of m×n antenna elements, which are each controlledby a separate signal conditioning circuit, in this embodiment. Asindicated by the ellipses, the communication system 110 can beimplemented with any suitable number of antenna elements and signalconditioning circuits.

With respect to signal transmission, the signal conditioning circuitscan provide transmit signals to the antenna array 102 such that signalsradiated from the antenna elements combine using constructive anddestructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction away from the antenna array 102.

In the context of signal reception, the signal conditioning circuitsprocess the received signals (for instance, by separately controllingreceived signal phases) such that more signal energy is received whenthe signal is arriving at the antenna array 102 from a particulardirection. Accordingly, the communication system 110 also providesdirectivity for reception of signals.

The relative concentration of signal energy into a transmit beam or areceive beam can be enhanced by increasing the size of the array. Forexample, with more signal energy focused into a transmit beam, thesignal is able to propagate for a longer range while providingsufficient signal level for RF communications. For instance, a signalwith a large proportion of signal energy focused into the transmit beamcan exhibit high effective isotropic radiated power (EIRP).

In the illustrated embodiment, the transceiver 105 provides transmitsignals to the signal conditioning circuits and processes signalsreceived from the signal conditioning circuits. As shown in FIG. 3A, thetransceiver 105 generates control signals for the signal conditioningcircuits. The control signals can be used for a variety of functions,such as controlling the gain and phase of transmitted and/or receivedsignals to control beamforming.

FIG. 3B is a schematic diagram of one example of beamforming to providea transmit beam. FIG. 3B illustrates a portion of a communication systemincluding a first signal conditioning circuit 114 a, a second signalconditioning circuit 114 b, a first antenna element 113 a, and a secondantenna element 113 b.

Although illustrated as included two antenna elements and two signalconditioning circuits, a communication system can include additionalantenna elements and/or signal conditioning circuits. For example, FIG.3B illustrates one embodiment of a portion of the communication system110 of FIG. 3A.

The first signal conditioning circuit 114 a includes a first phaseshifter 130 a, a first power amplifier 131 a, a first low noiseamplifier (LNA) 132 a, and switches for controlling selection of thepower amplifier 131 a or LNA 132 a. Additionally, the second signalconditioning circuit 114 b includes a second phase shifter 130 b, asecond power amplifier 131 b, a second LNA 132 b, and switches forcontrolling selection of the power amplifier 131 b or LNA 132 b.

Although one embodiment of signal conditioning circuits is shown, otherimplementations of signal conditioning circuits are possible. Forinstance, in one example, a signal conditioning circuit includes one ormore band filters, duplexers, and/or other components.

In the illustrated embodiment, the first antenna element 113 a and thesecond antenna element 113 b are separated by a distance d.Additionally, FIG. 3B has been annotated with an angle θ, which in thisexample has a value of about 90° when the transmit beam direction issubstantially perpendicular to a plane of the antenna array and a valueof about 0° when the transmit beam direction is substantially parallelto the plane of the antenna array.

By controlling the relative phase of the transmit signals provided tothe antenna elements 113 a, 113 b, a desired transmit beam angle θ canbe achieved. For example, when the first phase shifter 130 a has areference value of 0°, the second phase shifter 130 b can be controlledto provide a phase shift of about −2πf(d/v)cos θ radians, where f is thefundamental frequency of the transmit signal, d is the distance betweenthe antenna elements, v is the velocity of the radiated wave, and π isthe mathematic constant pi.

In certain implementations, the distance d is implemented to be about½λ, where λ is the wavelength of the fundamental component of thetransmit signal. In such implementations, the second phase shifter 130 bcan be controlled to provide a phase shift of about −π cos θ radians toachieve a transmit beam angle θ.

Accordingly, the relative phase of the phase shifters 130 a, 130 b canbe controlled to provide transmit beamforming. In certainimplementations, a baseband processor and/or a transceiver (for example,the transceiver 105 of FIG. 3A) controls phase values of one or morephase shifters and gain values of one or more controllable amplifiers tocontrol beamforming.

FIG. 3C is a schematic diagram of one example of beamforming to providea receive beam. FIG. 3C is similar to FIG. 3B, except that FIG. 3Cillustrates beamforming in the context of a receive beam rather than atransmit beam.

As shown in FIG. 3C, a relative phase difference between the first phaseshifter 130 a and the second phase shifter 130 b can be selected toabout equal to −2πf(d/v)cos θ radians to achieve a desired receive beamangle θ. In implementations in which the distance d corresponds to about½λ, the phase difference can be selected to about equal to −π cos θradians to achieve a receive beam angle θ.

Although various equations for phase values to provide beamforming havebeen provided, other phase selection values are possible, such as phasevalues selected based on implementation of an antenna array,implementation of signal conditioning circuits, and/or a radioenvironment.

Examples of Multi-Antenna Systems with Analog Signal Combining atBaseband

Antenna arrays can be used in a wide variety of applications. Forexample, antenna arrays can be used to transmit and/or receive radiofrequency (RF) signals in base stations, network access points, mobilephones, tablets, laptops, computers, and/or other communicationsdevices. Moreover, in certain implementations, separate antenna arraysare deployed for transmission and reception.

Communications devices that utilize millimeter wave carriers (forinstance, 30 GHz to 300 GHz), centimeter wave carriers (for instance, 3GHz to 30 GHz), and/or other carrier frequencies can employ an antennaarray to provide beam forming, MIMO communications, and/or diversitycommunications.

Apparatus and methods for multi-antenna communications are provided. Incertain embodiments, a communication system includes an antenna arrayincluding a plurality of antenna elements, and a plurality of RF circuitchannels each coupled to a corresponding one of the antenna elements.The plurality of RF circuit channels generate two or more analogbaseband signals in response to the antenna array receiving a radiowave. The communication system further includes a controllableamplification and combining circuit that generates two or more amplifiedanalog baseband signals based on amplifying each of the two or moreanalog baseband signals with a separately controllable gain, and thatcombines the two or more amplified analog baseband signals to generate acombined analog baseband signal.

The controllable amplification and combining circuit can providedifferent amounts of amplification to each of the analog basebandsignals. In such implementations, the combined analog baseband signalcorresponds to a weighted sum of the two or more analog basebandsignals.

In certain implementations, the controllable amplification and combiningcircuit is configurable in multiple modes including a first mode inwhich the two or more amplified analog baseband signals are combined togenerate the combined analog baseband signal, and a second mode in whichthe two or more amplified analog baseband signals are outputted withoutcombining. The amount of amplification provided can vary from signal tosignal in the second mode.

Implementing the controllable amplification and combining circuit withmultiple operating modes can provide a number of advantages, includingallowing both beamforming in the first mode and diversity communicationsin the second mode. This in turn can lead to higher signal-to-noiseratio (SNR), communication at greater distances, higher data rates,and/or communication in harsher radio environments. Furthermore, DCoffset correction can be provided for each amplified analog basebandsignal, thereby providing DC offset correction for each channel withreduced complexity and/or with higher accuracy.

In certain implementations, each RF circuit channel receives one or moreclock signals for downconversion from a corresponding local oscillator.Additionally, the local oscillators each receive a common timingreference signal for phase and/or frequency detection. By implementingthe communication system in this manner, a number of advantages can berealized, including, but not limited to, lower current consumption inthe local oscillators and/or uncorrelated noise between channels afterRF.

In certain implementations, phase shifting is performed at least in partat intermediate frequency (IF). For example, each RF circuit channel caninclude an RF-to-IF mixer for downconverting a received RF signal togenerate an IF signal (which can be an RF signal of lower frequency thanthe received RF signal), and an IF phase shifter for providing a desiredamount of phase shift to the IF signal. Performing phase shifting atleast in part at IF can provide a number of advantages, including, forexample, lower loss and/or relaxed design constraints arising fromperforming phase shifting at decreased frequency relative to that of thereceived radio wave.

FIG. 4A is a schematic diagram of one embodiment of a communicationsystem 180 operating in a first mode. The communication system 180includes an antenna array 181, RF circuit channels 182, and acontrollable amplification and combining circuit 183.

The RF circuit channels 182 each receive an RF signal from acorresponding antenna element of the antenna array 181 in response to aradio wave. Additionally, the RF circuit channels 182 process the RFsignals to generate multiple analog baseband signals. Thus, the RFcircuit channels 182 operate in part to provide downconversion. Incertain implementations, the RF circuit channels 182 process k RFsignals and to generate l analog baseband signals, where k and l areeach an integer greater than or equal to 2. The integers k and l can bethe same or different.

As shown in FIG. 4A, the controllable amplification and combiningcircuit 183 receives the analog baseband signals, gain control signalsfor controlling an amount of gain provided to each of the analogbaseband signals, and a mode control signal. The mode control signaloperates to control the communication system 180 in one of multiplemodes including at least a first mode and a second mode.

In FIG. 4A, the communication system 180 is depicted operating in thefirst mode, in which the controllable amplification and combiningcircuit 183 combines the analog baseband signals to generate a combinedanalog baseband signal. When combining the analog baseband signals, thecontrollable amplification and combining circuit 183 provides gain toeach analog baseband signal based on the indicated amount of gain by thegain control signals. The settings for gain can be the same or differentfor each analog baseband signal, and thus the combined analog basebandsignal corresponds to a weighted sum of the analog baseband signals.

FIG. 4B is a schematic diagram of the communication system 180 of FIG.4B operating in a second mode.

When operating in the second mode, the communication system 180 outputsmultiple analog baseband output signals without combining. The analogbaseband output signals are also referred to as amplified analogbaseband signals.

With reference to FIGS. 4A and 4B, the communication system 180 isoperable in a first mode in which the analog baseband signals areamplified and combined to generate the combined analog baseband signal,and a second mode in which the analog baseband signals are amplified andoutputted without analog combining at baseband. The amount ofamplification provided the analog baseband signals can also vary fromsignal to signal in the second mode.

Implementing the controllable amplification and combining circuit 183with multiple operating modes can provide a number of advantages,including allowing both beamforming in the first mode and diversitycommunications in the second mode. This in turn can lead to higher SNR,communication at greater distances, higher data rates, and/orcommunication in harsher radio environments. Furthermore, DC offsetcorrection can be provided for each amplified analog baseband signal,thereby providing DC offset correction for each channel with reducedcomplexity and/or with higher accuracy.

FIG. 5A is a schematic diagram of a communication system 200 accordingto one embodiment. The communication system 200 includes an antennaarray 201, RF circuit channels 202 a, 202 b, . . . 202 n, a controllableamplification and combining circuit 203, a data conversion and signalprocessing circuit 204, local oscillators (LOs) 207 a, 207 b, . . . 207n, and I/Q dividers 208 a, 208 b, . . . 208 n. Although circuitry forthree signal channels is depicted, more or fewer components can beincluded as indicated by the ellipses.

The antenna array 201 includes antenna elements 212 a, 212 b, . . . 212n. Although three antenna elements are illustrated, the communicationsystem 200 can include more or fewer antenna elements as indicated bythe ellipses. The antenna elements 212 a, 212 b, . . . 212 n can beimplemented in a wide variety of ways, including, but not limited to,using patch antenna elements, dipole antenna elements, ceramicresonators, stamped metal antennas, and/or laser direct structuringantennas. Moreover, antenna elements can be arrayed in other patterns orconfigurations, including, for instance, rectangular arrays, lineararrays, and/or arrays using non-uniform arrangements of antennaelements.

In the illustrated embodiment, the RF circuit channel 202 a includes anRF controllable gain and phase circuit 214 a, an RF-to-IF mixer 216 a,an IF controllable gain and phase circuit 218 a, an I-path mixer 221 a,and a Q-path mixer 222 a. Similarly, the RF circuit channel 202 bincludes an RF controllable gain and phase circuit 214 b, an RF-to-IFmixer 216 b, an IF controllable gain and phase circuit 218 b, an I-pathmixer 221 b, and a Q-path mixer 222 b. Likewise, the RF circuit channel202 n includes an RF controllable gain and phase circuit 214 n, anRF-to-IF mixer 216 n, an IF controllable gain and phase circuit 218 n,an I-path mixer 221 n, and a Q-path mixer 222 n.

Although one example implementation of the RF circuit channels 202 a,202 b, . . . 202 n is shown, the teachings herein are applicable to RFcircuit channels implemented in a wide variety of ways.

In the illustrated embodiment, the LOs 207 a, 207 b, . . . 207 ngenerate clock signals for the RF-to-IF mixers 216 a, 216 b, . . . 216n, respectively. Additionally, the LOs 207 a, 207 b, . . . 207 n eachreceive a common timing reference (REF), which is used by each LO forphase and/or frequency detection. By providing a common timing referenceto distributed LOs, reduced current consumption is realized relative toan implementation using a single LO that distributes a common clocksignal to the mixers. Moreover, the communication system 200 can haveuncorrelated phase noise after RF, and thus operates with superior SNRrelative to a communication system operating with fully synchronizedtiming.

As shown in FIG. 5A, the LOs 207 a, 207 b, . . . 207 n also provideclock signals to the I/Q dividers 208 a, 208 b, . . . 208 n,respectively. The clock signals provided to the I/Q dividers 208 a, 208b, . . . 208 n can be the same or different as the clock signalsprovided to the RF-to-IF mixers 216 a, 216 b, . . . 216 n. The I/Qdividers 208 a, 208 b, . . . 208 n operate to provide frequency divisionto generate clock signals suitable for controlling the I-path mixers 221a, 221 b, . . . 221 n and Q-path mixers 222 a, 222 b, . . . 222 n.

As shown in FIG. 5A, each of the RF circuit channels 202 a, 202 b, . . .202 n outputs an analog baseband signal including an I-component and aQ-component. For example, the RF circuit channel 202 a outputs an analogbaseband signal I_(a), Q_(a), the RF circuit channel 202 b outputs ananalog baseband signal I_(b), Q_(b), and the RF circuit channel 202 noutputs an analog baseband signal I_(n), Q_(n).

The controllable amplification and combining circuit 203 processes theanalog baseband signals from the RF circuit channels 202 a, 202 b, . . .202 n to generate one or more analog signals for the data conversion andsignal processing circuit 204.

In certain implementations, the controllable amplification and combiningcircuit 203 is configurable in multiple modes. The multiple modesinclude a first mode in which the analog baseband signals are eachamplified by a separately controllable gain to generate amplified analogbaseband signals, which are combined to generate a combined analogbaseband signal for the data conversion and signal processing circuit203. In this example, the combined analog baseband signal includes I andQ components, and thus is implemented using quadrature signaling. Themultiple modes further include a second mode in which the analogbaseband signals are outputted to the data conversion and signalprocessing circuit 203 without combining. When operating in the firstmode and/or the second mode, the controllable amplification andcombining circuit 203 can provide a controllable amount of gain to eachanalog baseband signal. Thus, the amount of amplification provided canvary from signal to signal.

Implementing the controllable amplification and combining circuit 203with multiple modes allows the communication system 200 to providebeamforming in the first mode and diversity communications in the secondmode. Furthermore, DC offset correction can be provided for each inputto the controllable amplification and combining circuit 203, therebyproviding DC offset correction with reduced complexity and/or withhigher accuracy.

In the illustrated embodiment, the IF controllable gain and phasecircuits 218 a, 218 b, . . . 218 n are included to provide phaseshifting at least in part at IF. Performing phase shifting at least inpart at IF can provide a number of advantages, including, for example,lower loss and/or relaxed design constraints arising from performingphase shifting at lower frequency relative to the frequency of the radiowave received by the antenna array 201.

FIG. 5B is a schematic diagram of a communication system 230 accordingto another embodiment. The communication system 230 includes an antennaarray 201, RF circuit channels 232 a, 232 b, . . . 232 n, a variablegain amplifier (VGA) and combiner circuit 233, a MIMO processing circuit234, a timing reference generator 235, LOs 237 a, 237 b, . . . 237 n,and I/Q dividers 238 a, 238 b, . . . 238 n. Although circuitry for threesignal channels is depicted, more or fewer components can be included asindicated by the ellipses.

The communication system 230 of FIG. 5B is similar to the communicationsystem 200 of FIG. 5A, except that the communication system 230illustrates specific implementations of certain circuitry.

For example, as shown in FIG. 5B, the RF circuit channel 232 a includesan LNA 241 a, an RF VGA phase shifter 242 a, an RF-to-IF mixer 246 a, anIF automatic gain control (AGC) phase shifter 248 a, an I-path mixer 251a, and a Q-path mixer 252 a. Likewise, the RF circuit channel 232 bincludes an LNA 241 b, an RF VGA phase shifter 242 b, an RF-to-IF mixer246 b, an IF AGC phase shifter 248 b, an I-path mixer 251 b, and aQ-path mixer 252 b. Similarly, the RF circuit channel 232 n includes anLNA 241 n, an RF VGA phase shifter 242 n, an RF-to-IF mixer 246 n, an IFAGC phase shifter 248 n, an I-path mixer 251 n, and a Q-path mixer 252n.

Furthermore, the LO 237 a includes a phase and/or frequency detector(PFD) and charge pump (CP) 261 a, a loop filter 263 a, a voltagecontrolled oscillator (VCO) 264 a, an output divider 265 a (1 overinteger M, in this example), a feedback divider 266 a (N/N+1, in thisexample), and a sigma delta (ΣΔ) modulator 267 a. Similarly, the LO 237b includes a PFD/CP 261 b, a loop filter 263 b, a VCO 264 b, an outputdivider 265 b, a feedback divider 266 b, and a ΣΔ modulator 267 b.Likewise, the LO 237 n includes a PFD/CP 261 n, a loop filter 263 n, aVCO 264 n, an output divider 265 n, a feedback divider 266 n, and a ΣΔmodulator 267 n.

The I/Q divider 238 a includes a first divider 271 a (divide by 2, inthis example) and a second divider 272 a (divide by 2, in this example).Likewise, the I/Q divider 238 b includes a first divider 271 b and asecond divider 272 b. Similarly, the I/Q divider 238 n includes a firstdivider 271 n and a second divider 272 n.

With continuing reference to FIG. 5B, the VGA and combiner circuit 233includes VGA combining circuits 281 a, 281 b, . . . 281 n. Additionally,the MIMO processing circuit 234 includes ADCs 284 a, 284 b, . . . 284 n.In certain implementations, the ADCs 284 a, 284 b, . . . 284 n includean I-path ADC and a Q-path ADC for each RF circuit channel.

FIG. 6A is a schematic diagram of one embodiment of a controllableamplification and combining circuit 300 in a first mode of operation.FIG. 6B is a schematic diagram of the controllable amplification andcombining circuit 300 of FIG. 6A in a second mode of operation. Thecontrollable amplification and combining circuit 300 is coupled to theADCs 308 a, 308 b, . . . 308 n of a data conversion and signalprocessing circuit, such as a MIMO processing circuit. The analogsignals outputted from the controllable amplification and combiningcircuit 300 are associated with channels Ch_(a), Ch_(b), . . . Ch_(n).

Although one embodiment of a controllable amplification and combiningcircuit is shown, the teachings herein are applicable to controllableamplification and combining circuits implemented in a wide variety ofways.

With reference to FIGS. 6A and 6B, the controllable amplification andcombining circuit 300 includes controllable gain input amplifiers 301 a,301 b, . . . 301 n, DC offset compensation circuits 302 a, 302 b, . . .302 n, selection circuits 303 a, 303 b, . . . 303 n, first outputbuffers 305 a, 305 b, . . . 305 n, and second output buffers 306 a, 306b, . . . 306 n. The output buffers can have fixed or controllable gain.The selection circuits 303 a, 303 b, . . . 303 n are also collectivelyreferred to herein as a signal selector.

The controllable amplification and combining circuit 300 is implementeddifferentially, in this embodiment. However, other types of signalingcan be used, such as single-ended signaling or a combination ofdifferential and signal-ended signaling.

The controllable gain input amplifiers 301 a, 301 b, . . . 301 n providecontrollable amplification to input signals In_(a), In_(b), . . .In_(n). The gain provided by the amplifiers 301 a, 301 b, . . . 301 ncan be controlled in a wide variety of ways, including, but not limitedto, by a transceiver or radio frequency integrated circuit (RFIC) overan interface, such as a MIPI RFFE interface. In certain implementations,the input signals In_(a), In_(b), . . . In_(n) correspond to I-pathsignals (for instance, I_(a), I_(b), . . . I_(n) of FIG. 5A or 5B), andanother group of controllable gain input amplifiers and associatedcircuits process Q-path signals (for instance, Q_(a), Q_(b), . . . Q_(n)of FIG. 5A or 5B). Accordingly, in certain implementations multipleinstantiations of the controllable amplification and combining circuit300 are included.

A state of the selection circuits 303 a, 303 b, . . . 303 n changesbased on a mode of the controllable amplification and combining circuit300. The selected mode can be controlled in a wide variety of ways,including, but not limited to, by a transceiver or RFIC over a MIPI RFFEinterface or other suitable interface.

As shown in FIG. 6A, the controllable amplification and combiningcircuit 300 generates a combined analog baseband signal 309 in the firstmode. Since the gain of the controllable gain input amplifiers 301 a,301 b, . . . 301 n can be separately controlled, the combined analogbaseband signal 309 is generated by a weighted sum of the input signalsIn_(a), In_(b), . . . In_(n), in this embodiment. In certainimplementations, unused ADCs are turned off in the first mode toconserve power. For example, as shown in FIG. 6A, the ADC that is usedcan have an enable signal (EN) set to an enabled state (EN=1, in thisexample), while the ADCs that are unused can have the enable signal setto a disabled state (EN=0, in this example). In certain implementations,the ADCs are enabled or disabled using data receiver over a chipinterface.

As shown in FIG. 6B, the controllable amplification and combiningcircuit 300 generates analog baseband signals 321 a, 321 b, . . . 321 nin the second mode. In certain implementations, the controllableamplification and combining circuit 300 separately controls the gain ofthe analog baseband signals 321 a, 321 b, . . . 321 n.

Implementing a controllable amplification and combining circuit withmultiple modes provides a number of advantages, including allowing bothbeamforming in the first mode and diversity communications in the secondmode. This in turn can lead to higher SNR, communication at greaterdistances, communication at greater data rates, and/or communication inharsher radio environments.

Furthermore, DC offset correction can be provided for each input to thecontrollable amplification and combining circuit, thereby providing DCoffset correction with reduced complexity and/or with higher accuracy.For example, as shown in FIG. 6B, the DC offset compensation circuits302 a, 302 b, . . . 302 n provide a differential output signal tocompensate for a DC offset of Ch_(a), Ch_(b), . . . Ch_(n),respectively. The amount of DC offset compensation provided by each ofthe DC offset compensation circuits 302 a, 302 b, . . . 302 n can becontrolled in a wide variety of ways, including, but not limited to, bya transceiver or RFIC over a MIPI RFFE interface or other suitableinterface.

In certain embodiments, the controllable amplification and combiningcircuit 300 is implemented on a semiconductor die, which can beincorporated into a radio frequency module. In certain implementations,the ADCs 308 a, 308 b, . . . 308 n are also included on thesemiconductor die. In other implementations, the ADCs 308 a, 308 b, . .. 308 n are included a second semiconductor die, which can beincorporated with the first semiconductor die in a multi-chip module.

FIG. 7 is a schematic diagram of one embodiment of a portion of thecontrollable amplification and combining circuit 300 of FIGS. 6A and 6B.The illustrated circuitry 350 includes a first pair of load resistors351 a-351 b, a second pair of load resistors 352 a-352 b, a first pairof selection transistors 353 a-353 b, a second pair of selectiontransistors 354 a-354 b, a first pair of signal amplificationtransistors 361 a-361 b, a second pair of signal amplificationtransistors 362 a-362 b, a third pair of signal amplificationtransistors 363 a-363 b, a fourth pair of signal amplificationtransistors 364 a-364 b, a first weighted resistor 371, a secondweighted resistor 372, a third weighted resistor 373, a fourth weightedresistor 374, a first pair of bias current sources 381 a-381 b, a secondpair of bias current sources 382 a-382 b, a third pair of bias currentsources 383 a-383 b, a fourth pair of bias current sources 384 a-384 b,a first pair of gain control switches 391 a-391 b, a second pair of gaincontrol switches 392 a-392 b, a third pair of gain control switches 393a-393 b, a fourth pair of gain control switches 394 a-394 b, and a DCoffset compensation circuit 302. The circuitry 350 is powered by asupply voltage VDD and ground.

The circuitry 350 illustrates one implementation of a controllable gaininput amplifier, a selection circuit, and a DC offset compensationcircuit. For example, the circuitry 350 can be used to implement thecontrollable gain input amplifier 301 a, the selection circuit 303 a,and the DC offset compensation circuit 302 a of FIGS. 6A and 6B.Additionally, multiple instantiations of the circuitry 350 can be usedto implement the controllable amplification and combining circuit 300 ofFIGS. 6A and 6B. Although one embodiment of suitable circuitry forimplementing a portion of a controllable amplification and combiningcircuit is shown, the teachings herein are applicable to controllableamplification and combining circuits implemented in a wide variety ofways.

The selection signals Sel_0 and Sel_1 operate to select the first pairof selection transistors 353 a-353 b or the second pair of selectiontransistors 354 a-354 b, thereby providing connection to a firstdifferential output Vout_0_p, Vout_0_n or to a second differentialoutput Vout_1_p, Vout_1_n. The selection signals Sel_0 and Sel_1 operateto control the mode of a controllable amplification and combiningcircuit between the first mode and the second mode, as discussed above.

The weighted resistors 371-374 are binary weighted, in this embodiment.Additionally, one or more of the gain control signals Gain_1, Gain_2,Gain_3, Gain_4 can be activated to provide a desired amount of gain tothe differential input signal Vin_p, Vin_n. Although an example withfour gain stages is shown, more or fewer gain stages can be included.

The DC offset compensation circuit 302 outputs a differential outputsignal Vout_dc_p, Vout_dc_n to provide a DC offset for compensation. Theamount of DC offset is controlled by a control signal CTL, in thisexample.

FIG. 8 is a schematic diagram of one embodiment of a DC offsetcompensation circuit 400. The DC offset compensation circuit 400includes a pair of load resistors 401 a-401 b, a pair of cascodetransistors 402 a-402 b, a first pair of compensation controltransistors 411 a-411 b, a second pair of compensation controltransistors 412 a-412 b, a third pair of compensation controltransistors 413 a-413 b, a fourth pair of compensation controltransistors 414 a-414 b, a first pair of weighted bias current sources421 a-421 b, a second pair of weighted bias current sources 422 a-422 b,a third pair of weighted bias current sources 423 a-423 b, a fourth pairof weighted bias current sources 424 a-424 b, a first pair of selectionswitches 431 a-431 b, a second pair of selection switches 432 a-432 b, athird pair of selection switches 433 a-433 b, and a fourth pair ofselection switches 434 a-434 b. The circuitry 350 is powered by a supplyvoltage VDD and ground. As shown in FIG. 8 , each pair of compensationcontrol transistors receives a bias voltage Vbias, and the pair ofcascode transistors 402 a-402 b receives a cascode bias voltageVbias_csc.

The first pair of selection switches 431 a-431 b is controlled by afirst pair of complementary control signals Off_1, Off_1 b. Likewise,the second pair of selection switches 432 a-432 b is controlled by asecond pair of complementary control signals Off_2, Off_2 b. Similarly,the third pair of selection switches 433 a-433 b is controlled by athird pair of complementary control signals Off_3, Off_3 b. Furthermore,the fourth pair of selection switches 434 a-434 b is controlled by afourth pair of complementary control signals Off_4, Off_4 b.

When a particular current source is activated by a particular selectionswitch, current from the bias current source flows through thecorresponding cascode transistor 402 a or 402 b and load resistor 401 aor 401 b to control the differential output voltage Vout_dc_p,Vout_dc_n. Although an example with four pairs of weighted bias currentsources is shown, other implementations are possible, such asconfigurations using more or fewer current sources. In this embodiment,the pairs of weighted bias current sources are binary weighted.

FIG. 9A is a schematic diagram of a communication system 500 accordingto another embodiment. The communication system 500 includes an antennaarray 501, RF circuit channels 522 a, 522 b, 522 c, 522 d, . . . 522n−1, 522 n, a timing reference generator 235, LOs 237 a, 237 b, 237 c,237 d, . . . 237 n−1, 237 n, I/Q dividers 238 a, 238 b, . . . 238 n/2,IF combiners 531 a, 531 b, . . . 531 n/2, I/Q downconverters 532 a, 532b, . . . 532 n/2, a VGA and combiner circuit 533, and a MIMO processingcircuit 534. The antenna array 501 includes antenna elements 512 a, 512b, 512 c, 512 d, . . . 512 n−1, 512 n. Additionally, the VGA andcombiner circuit 233 includes VGAs 282 a, 282 b, . . . 282 n/2.Furthermore, the MIMO processing circuit includes ADCs 284 a, 284 b, . .. 284 n/2. In this embodiment, n is an even integer, for instance, aninteger of at least 2, or more particularly, 4 or greater.

The communication system 500 of FIG. 9A is similar to the communicationsystem 230 of FIG. 5B, except that the communication system 500 includesthe RF combiners 531 a, 531 b, . . . 531 n, which provide combining atIF for signals received from groups of antenna elements (groups of two,in this example). In certain implementations, two or more signalsreceived from the antenna array 201 are combined at IF.

After combining at IF and subsequent downconversion, the analog basebandsignals are provided to the VGA and combiner circuit 533, which canprovide controllable amplification and combining as described above.

FIG. 9B is a schematic diagram of one embodiment of a portion 9B of thecommunication system 500 of FIG. 9A. The illustrated circuitry includesthe timing reference generator 235, the first antenna element 512 a, thesecond antenna element 512 b, the first RF circuit channel 522 a, thesecond RF circuit channel 522 b, the first LO 237 a, the second LO 237b, the I/F combiner 531 a, the I/Q downconverter 532 a, the I/Q divider238 a, the VGA 281 a, and the ADC 284 a.

As shown in FIG. 9B, the first RF circuit channel 522 a includes the LNA241 a, the RF VGA phase shifter 242 a, the RF-to-IF mixer 246 a, and theIF AGC phase shifter 248 a. Additionally, the second RF circuit channel522 b includes the LNA 241 b, the RF VGA phase shifter 242 b, theRF-to-IF mixer 246 b, and the IF AGC phase shifter 248 b. The I/Qdownconverter 532 a includes the I-path mixer 251 a and the Q-path mixer252 a. The I/Q divider 238 a includes the first divider 271 a and thesecond divider 272 a. The LO 237 a includes the PFD/CP 261 a, the loopfilter 263 a, the VCO 264 a, the output divider 265 a, the feedbackdivider 266 a, and the ΣΔ modulator 267 a. Similarly, the LO 237 bincludes the PFD/CP 261 b, the loop filter 263 b, the VCO 264 b, theoutput divider 265 b, the feedback divider 266 b, and the ΣΔ modulator267 b.

FIG. 10 is a schematic diagram of one embodiment of a mobile device 800.The mobile device 800 includes a baseband system 801, a transceiver 802,a front end system 803, antennas 804, a power management system 805, amemory 806, a user interface 807, and a battery 808.

The mobile device 800 can be used communicate using a wide variety ofcommunications technologies, including, but not limited to, 2G, 3G, 4G(including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (forinstance, WiFi), WPAN (for instance, Bluetooth and ZigBee), WMAN (forinstance, WiMax), and/or GPS technologies.

The transceiver 802 generates RF signals for transmission and processesincoming RF signals received from the antennas 804. It will beunderstood that various functionalities associated with the transmissionand receiving of RF signals can be achieved by one or more componentsthat are collectively represented in FIG. 10 as the transceiver 802. Inone example, separate components (for instance, separate circuits ordies) can be provided for handling certain types of RF signals.

The front end system 803 aids is conditioning signals transmitted toand/or received from the antennas 804. In the illustrated embodiment,the front end system 803 includes antenna tuning circuitry 810, poweramplifiers (PAs) 811, low noise amplifiers (LNAs) 812, filters 813,switches 814, and signal splitting/combining circuitry 815. However,other implementations are possible.

For example, the front end system 803 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals (for instance, diplexing ortriplexing), or some combination thereof.

In certain implementations, the mobile device 800 supports carrieraggregation, thereby providing flexibility to increase peak data rates.Carrier aggregation can be used for both Frequency Division Duplexing(FDD) and Time Division Duplexing (TDD), and may be used to aggregate aplurality of carriers or channels. Carrier aggregation includescontiguous aggregation, in which contiguous carriers within the sameoperating frequency band are aggregated. Carrier aggregation can also benon-contiguous, and can include carriers separated in frequency within acommon band or in different bands.

The antennas 804 can include antennas used for a wide variety of typesof communications. For example, the antennas 804 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 804 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The mobile device 800 can operate with beamforming in certainimplementations. For example, the front end system 803 can includeamplifiers having controllable gain and phase shifters havingcontrollable phase to provide beam formation and directivity fortransmission and/or reception of signals using the antennas 804. Forexample, in the context of signal transmission, the amplitude and phasesof the transmit signals provided to the antennas 804 are controlled suchthat radiated signals from the antennas 804 combine using constructiveand destructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction. In the context of signal reception, the amplitude andphases are controlled such that more signal energy is received when thesignal is arriving to the antennas 804 from a particular direction. Incertain implementations, the antennas 804 include one or more arrays ofantenna elements to enhance beamforming.

The baseband system 801 is coupled to the user interface 807 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 801 provides the transceiver 802with digital representations of transmit signals, which the transceiver802 processes to generate RF signals for transmission. The basebandsystem 801 also processes digital representations of received signalsprovided by the transceiver 802. As shown in FIG. 10 , the basebandsystem 801 is coupled to the memory 806 of facilitate operation of themobile device 800.

The memory 806 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of themobile device 800 and/or to provide storage of user information.

The power management system 805 provides a number of power managementfunctions of the mobile device 800. In certain implementations, thepower management system 805 includes a PA supply control circuit thatcontrols the supply voltages of the power amplifiers 811. For example,the power management system 805 can be configured to change the supplyvoltage(s) provided to one or more of the power amplifiers 811 toimprove efficiency, such as power added efficiency (PAE).

As shown in FIG. 10 , the power management system 805 receives a batteryvoltage from the battery 808. The battery 808 can be any suitablebattery for use in the mobile device 800, including, for example, alithium-ion battery.

FIG. 11A is a perspective view of one embodiment of a module 940 thatoperates with beamforming. FIG. 11B is a cross-section of the module 940of FIG. 11A taken along the lines 11B-11B.

The module 940 includes a laminated substrate or laminate 941, asemiconductor die or IC 942 (not visible in FIG. 11A), surface mountdevices (SMDs) 943 (not visible in FIG. 11A), and an antenna arrayincluding antenna elements 951 a 1, 951 a 2, 951 a 3 . . . 951 an, 951 b1, 951 b 2, 951 b 3 . . . 951 bn, 951 c 1, 951 c 2, 951 c 3 . . . 951cn, 951 m 1, 951 m 2, 951 m 3 . . . 951 mn.

Although one embodiment of a module is shown in FIGS. 11A and 11B, theteachings herein are applicable to modules implemented in a wide varietyof ways. For example, a module can include a different arrangement ofand/or number of antenna elements, dies, and/or surface mount devices.Additionally, the module 940 can include additional structures andcomponents including, but not limited to, encapsulation structures,shielding structures, and/or wirebonds.

The antenna elements antenna elements 951 a 1, 951 a 2, 951 a 3 . . .951 an, 951 b 1, 951 b 2, 951 b 3 . . . 951 bn, 951 c 1, 951 c 2, 951 c3 . . . 951 cn, 951 m 1, 951 m 2, 951 m 3 . . . 951 mn are formed on afirst surface of the laminate 941, and can be used to receive and/ortransmit signals, based on implementation. Although a 4×4 array ofantenna elements is shown, more or fewer antenna elements are possibleas indicated by ellipses. Moreover, antenna elements can be arrayed inother patterns or configurations, including, for instance, arrays usingnon-uniform arrangements of antenna elements. Furthermore, in anotherembodiment, multiple antenna arrays are provided, such as separateantenna arrays for transmit and receive and/or for differentcommunication bands.

In the illustrated embodiment, the IC 942 is on a second surface of thelaminate 941 opposite the first surface. However, other implementationsare possible. In one example, the IC 942 is integrated internally to thelaminate 941.

In certain implementations, the IC 942 includes signal conditioningcircuits associated with the antenna elements 951 a 1, 951 a 2, 951 a 3. . . 951 an, 951 b 1, 951 b 2, 951 b 3 . . . 951 bn, 951 c 1, 951 c 2,951 c 3 . . . 951 cn, 951 m 1, 951 m 2, 951 m 3 . . . 951 mn. In oneembodiment, the IC 942 includes a serial interface, such as a mobileindustry processor interface radio frequency front-end (MIPI RFFE) busand/or inter-integrated circuit (I²C) bus that receives data forcontrolling the signal conditioning circuits, such as the amount ofphase shifting provided by phase shifters. In another embodiment, the IC942 includes signal conditioning circuits associated with the antennaelements 951 a 1, 951 a 2, 951 a 3 . . . 951 an, 951 b 1, 951 b 2, 951 b3 . . . 951 bn, 951 c 1, 951 c 2, 951 c 3 . . . 951 cn, 951 m 1, 951 m2, 951 m 3 . . . 951 mn and an integrated transceiver.

The laminate 941 can include various structures including, for example,conductive layers, dielectric layers, and/or solder masks. The number oflayers, layer thicknesses, and materials used to form the layers can beselected based on a wide variety of factors, and can vary withapplication and/or implementation. The laminate 941 can include vias forproviding electrical connections to signal feeds and/or ground feeds ofthe antenna elements. For example, in certain implementations, vias canaid in providing electrical connections between signal conditioningcircuits of the IC 942 and corresponding antenna elements.

The antenna elements 951 a 1, 951 a 2, 951 a 3 . . . 951 an, 951 b 1,951 b 2, 951 b 3 . . . 951 bn, 951 c 1, 951 c 2, 951 c 3 . . . 951 cn,951 m 1, 951 m 2, 951 m 3 . . . 951 mn can correspond to antennaelements implemented in a wide variety of ways. In one example, thearray of antenna elements includes patch antenna element formed from apatterned conductive layer on the first side of the laminate 941, with aground plane formed using a conductive layer on opposing side of thelaminate 941 or internal to the laminate 941. Other examples of antennaelements include, but are not limited to, dipole antenna elements,ceramic resonators, stamped metal antennas, and/or laser directstructuring antennas.

The module 940 can be included a communication system, such as a mobilephone or base station. In one example, the module 940 is attached to aphone board of a mobile phone.

Applications

Some of the embodiments described above have provided examples ofdynamic antenna array management in connection with wirelesscommunications devices. However, the principles and advantages of theembodiments can be used for any other systems or apparatus that benefitfrom any of the circuits and systems described herein.

For example, antenna arrays can be included in various electronicdevices, including, but not limited to consumer electronic products,parts of the consumer electronic products, electronic test equipment,etc. Example electronic devices include, but are not limited to, a basestation, a wireless network access point, a mobile phone (for instance,a smartphone), a tablet, a television, a computer monitor, a computer, ahand-held computer, a personal digital assistant (PDA), a microwave, arefrigerator, an automobile, a stereo system, a disc player, a digitalcamera, a portable memory chip, a washer, a dryer, a copier, a facsimilemachine, a scanner, a multi-functional peripheral device, a wrist watch,a clock, etc. Further, the electronic devices can include unfinishedproducts.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“may,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A radio frequency system comprising: two or morefrequency downconverters configured to output two or more analogbaseband signals in response to receiving a plurality of radio frequencysignals from an antenna array; a controllable amplification andcombining circuit configured to generate two or more amplified analogbaseband signals based on amplifying each of the two or more analogbaseband signals with a separately controllable gain, the controllableamplification and combining circuit further configured, in a beamformingmode, to combine the two or more amplified analog baseband signals togenerate and output a combined analog baseband signal and, in anon-beamforming mode, to output the two or more amplified analogbaseband signals.
 2. The radio frequency system of claim 1 wherein thecontrollable amplification and combining circuit includes two or morecontrollable gain input amplifiers configured to amplify the two or moreanalog baseband signals to generate the two or more amplified analogbaseband signals.
 3. The radio frequency system of claim 2 wherein thecontrollable amplification and combining circuit further includes two ormore DC offset compensation circuits each configured to provide aseparately controllable DC offset correction to a corresponding one ofthe two or more controllable gain input amplifiers.
 4. The radiofrequency system of claim 1 further comprising two or moreanalog-to-digital converters each configured to receive a correspondingone of the two or more amplified analog baseband signals.
 5. The radiofrequency system of claim 1 further comprising two or more localoscillators configured to control downconversion of the two or morefrequency downconverters.
 6. The radio frequency system of claim 5wherein the two or more local oscillators each include aphase-locked-loop configured to receive a common timing referencesignal.
 7. A method of radio frequency communication, the methodcomprising: receiving a radio wave using a plurality of antenna elementsof an antenna array; generating two or more analog baseb and signalsusing a plurality of radio frequency circuit channels each coupled to acorresponding one of the plurality of antenna elements; amplifying eachof the two or more analog baseband signals with a separatelycontrollable gain using a controllable amplification and combiningcircuit; in a beamforming mode, combining the two or more amplifiedanalog baseband signals to generate a combined analog baseband signalusing the controllable amplification and combining circuit; and in anon-beamforming mode, to output the two or more amplified analogbaseband signals.
 8. The method of claim 7 further comprisingcompensating for a DC offset of each of the two or more amplified analogbaseband signals.
 9. The method of claim 7 further comprising convertingthe combined analog baseband signal to a digital signal.
 10. The methodof claim 7 further comprising performing phase shifting in each of theradio frequency circuit channels at an intermediate frequency that isless than a frequency of the radio wave.
 11. The method of claim 7further comprising generating a plurality of clock signals using aplurality of local oscillators operating with a common timing referencesignal, and providing each of the plurality of clock signals to acorresponding one of the plurality of radio frequency circuit channels.12. The method of claim 7 generating a first intermediate frequencysignal using a first radio frequency circuit channel of the plurality ofradio frequency circuit channels, generating a second intermediatefrequency signal using a second radio frequency circuit channel of theplurality of radio frequency circuit channels, and combining the firstintermediate frequency signal and the second intermediate frequencysignal.
 13. A communication system comprising: an antenna arrayincluding a plurality of antenna elements; a plurality of radiofrequency circuit channels each coupled to a corresponding one of theplurality of antenna elements, the plurality of radio frequency circuitchannels operable to generate two or more analog baseband signals inresponse to the antenna array receiving a radio wave; and a controllableamplification and combining circuit configured to generate two or moreamplified analog baseband signals based on amplifying each of the two ormore analog baseband signals with a separately controllable gain, thecontrollable amplification and combining circuit further configured, ina beamforming mode, to combine the two or more amplified analog basebandsignals to generate a combined analog baseband signal and, in anon-beamforming mode, to output the two or more amplified analogbaseband signals.
 14. The communication system of claim 13 wherein thecontrollable amplification and combining circuit includes two or morecontrollable gain input amplifiers configured to amplify the two or moreanalog baseband signals to generate the two or more amplified analogbaseband signals.
 15. The communication system of claim 14 wherein thecontrollable amplification and combining circuit further includes two ormore DC offset compensation circuits each configured to provide aseparately controllable DC offset correction to a corresponding one ofthe two or more controllable gain input amplifiers.
 16. Thecommunication system of claim 13 further comprising two or moreanalog-to-digital converters each configured to receive a correspondingone of the two or more amplified analog baseband signals.
 17. Thecommunication system of claim 13 further comprising two or morefrequency downconverters configured to output the two or more analogbaseband signals, and two or more local oscillators configured tocontrol downconversion of the two or more frequency downconverters. 18.The communication system of claim 17 wherein the two or more localoscillators each include a phase-locked-loop configured to receive acommon timing reference signal.